1. Field of Invention
This invention relates to block-and-tackle equipment and more particularly to a piece of equipment known as a “swivel base,” which is used on a large variety of sailing craft for the control and adjustment of various ropes and lines.
2. Description of Prior Art
On a typical sailing craft there are a number of ropes and lines that control the positioning and adjustment of sails, poles, and the various types of hardware needed for the operation of the craft. These lines are often secured by means of a device known as a cleat, which is affixed to the craft. The cleat is often mounted on a swivel base in order to facilitate the securing and releasing of the control lines. The swivel base allows for the rotation of the cleat so that the line can be adjusted from a variety of positions. A block or pulley is also mounted to the same swivel base to provide the line a fair lead into the cleat.
The basic form of the swivel base consists of a circular base mounted to the craft. The base supports an outwardly extending arm that can rotate about the base center. At the end of this arm is mounted the securing cleat. In addition, the pulley is mounted at the base center. A control line is passed through the pulley and then through the cleat. Adjusting the tension allows the control line to be either pulled in or let out; securing the line then effects the adjustment.
Prior art is illustrated by the Harken Swivel Base, U.S. Pat. No. 4,160,541 to Harken/Lawsen (1979). This device is known to have eliminated the problems associated with other similar devices; said problems include excessive free play in the lever arm, difficulty in releasing the line from the cleat, and excessive friction in the pivot bearing. There is one major problem that the Harken Swivel Base and all prior art swivel bases share: when the control line is secured by the cleat and the free end is released, the cleat end of the rotating arm is drawn toward the direction of load, typically the direction opposite from which the line was adjusted. In order to readjust the control line it, the operator must then reach around the swivel base, pick up the loose line, rotate the swivel base cleat back toward the direction of adjustment, and adjust the line.
The aforementioned problem occurs when, for example, a swivel base is used to control the mainsheet. Typically, the working end of the mainsheet in connected to the mainsail by means of a multiple-pulley system with lines running from the boom to the deck and then finally from the last boom pulley through the swivel base pulley and into the cleat. The boom is pushed toward the leeward side of the craft when the mainsheet is filled with wind. Typically, the person adjusting the mainsheet is positioned on the windward side of the craft opposite the pull of the boom. When the mainsheet is cleated and dropped, the swivel base cleat will rotate toward the boom and the leeward side of the craft. To reach and adjust the mainsheet, the operator must come down from the windward side of the craft, reach to the leeward side and pick up the mainsheet, pull the cleat back to the windward side, and then adjust the line.